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Re: Hot-blooded marine reptiles



On Tue, Jun 15th, 2010 at 11:42 AM, GSP1954@aol.com wrote:

> Endothermy merely means that the majority of body heat is generated 
> internally and does not necessarily imply a high metabolic rate is an
> animal can 
> use size and insulation to retain heat despite a reptilian resting
> metabolism, 
> or is exercising hard and long enough (such as larger sustained
> flight 
> insects).  Endothermy achieved via a normally elevated resting MR is
> tachymetabolism. Some tuna do have elevated resting metabolisms like
> birds and mammals. 

Good point. I was taking a rather mammal-centric view of endothermy (which 
isn't surprising, since 
I happen to be a mammal). 

Not all endotherms use the same means as mammals to achieve high body 
temperatures. If 
anything the mammalian condition is more of a fortuitous maladaptation, a bit 
like sickle-cell 
anaemia. Our poor old cells have to 'bail' so quickly to offset our ionically 
leaky cell membranes 
that high body temperatures are a symptom of that genetic 'mistake'. We've just 
made the best of 
a bad situation.

-- 
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Dann Pigdon
GIS Specialist                         Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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